ES2622557T3 - Temporary glass protection - Google Patents

Abstract

Glass substrate (1) coated with a continuous temporary protection layer (2) removable with water, said layer (2) being essentially a stack of discernible colloidal polymer particles (3).

Description

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DESCRIPTION

Temporary glass protection

The invention relates to the scope of glass protection layers.

During the manufacturing, processing, transport or storage stages of the glass, the glass surface is susceptible to being contaminated by various chemical or mechanically damaged agents. As an example, the transformation of glazing for the production of multiple insulating glazing (double or triple glazing) sometimes uses silicone-based joints or mastics. During a certain period, limited in time, after use, these joints tend to emit silicone vapors (monomers or oligomers that do not completely polymerize), which migrate to the surface of the glass and contaminate it. The silicone layer is extremely adherent to the glass due to its chemical similarity, which considerably complicates the cleaning stages of the glazing. It is therefore appropriate to limit contamination of silicones to the maximum.

This problem is especially important when it is intended to exploit the surface properties, in particular, the hydrophilic properties of layers deposited on the glass. It is known, for example, to deposit layers based on photocatalytic titanium oxide on the glass. European Patent Application No. 0.850.204 describes, for example, titanium oxide based layers which, due to their photocatalytic and photoinduced superhydrophilic properties, turn the surface of the self-cleaning and dirt-proof glass. The contamination in silicones is then capable of reducing the properties of the layer to nothing.

It is therefore important to have systems that temporarily protect the surface of the glass against this type of contamination.

It is known to protect the glass surface by peelable adhesive polymer films. These films can be deposited in a solid state (as for example in European Patent Application No. 1,610,940), or in a liquid state. In the latter case, illustrated for example by US Patent No. 5,866,199, a solution of polymers is deposited on the glass, after polymerization giving a continuous film adherent to the glass and which can be removed by peeling. The deposit of an adhesive film in a solid state nevertheless requires a rather complex installation of deposition. In addition, the peeling stage is often quite long and annoying and can leave traces of adhesives on the glass surface.

U.S. Pat. No. 2004/047997 describes a surface dirt-repellent treatment process that includes surface coating with particles of average diameter from 3 nm to 5 pm, having a surface energy of at least 20 mN / and can be made, in particular, of a polymeric material.

Some polymeric films obtained from a liquid phase were developed and can be removed by cleaning with the help of aqueous solutions. U.S. patent application No. 2002/0176988 describes for example the deposition of aqueous solutions or dispersions of different polymers, which form protective films that can be removed, for some, by washing with water or with the help of basic aqueous solutions. In general, the films obtained from aqueous solutions of polymers (for example of polyvinyl alcohol as described in the aforementioned US patent application No. 2002/0176988, or of acrylics as in the application of Patent No. WO 00/50354) are easily removable with water, since the polymer itself is water soluble. DE 4103283 describes a layer for stacking, transporting and storing glass that includes polymer balls of a diameter ranging from 0.03 to 0.1 mm. FR 254514 describes films containing soluble polymers and internal spacing particles, which may be acrylic balls. Such layers are however not very resistant and tend to be removed very quickly, for example under the action of rainwater. The protection is therefore too short and, to resume the example of multiple self-cleaning glazing, the protection layer is removed before the silicone seals have finished emitting silicone vapors. The prior art also describes films obtained from aqueous dispersions, therefore, water-insoluble polymers, which are more durable, but which require the use of basic solutions (for example based on ammonium hydroxide, such as described in US Patent Application No. 2002/0176988) or of organic products and special detergents that will move the film from the glass surface before cleaning with water (as described in the patent U.S. 5,453,459). These solutions or detergents are of delicate handling and / or are relatively harmful to the environment, and there is therefore a need for temporary protection layers that are both sufficiently durable and can be removed with water. The protective layer must, for example, be able to be easily removed by the occupants of the housing or a glassmaker after a few weeks or a month of exposure, therefore after the silicone gaskets have finished emitting silicone vapors.

The invention is therefore intended to propose a temporary protective layer of the glass that has sufficient durability but can be removed with the help of pure water.

For this purpose, the object of the invention is a glass substrate coated with a continuous temporary protection layer removable with water, said layer essentially consisting of a stack of discernible colloidal polymer particles. The polymeric particles preferably consist of a solid and water insoluble polymer.

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The object of the invention is also the process of obtaining said substrate. It is, in particular, a process of coating a glass substrate by a layer of continuous temporary protection, in which an aqueous dispersion of colloidal particles of at least one solid polymer is deposited on at least one surface of said substrate. insoluble in water, the layer thus obtained is dried at a temperature higher than the glass transition temperature of said at least poftmero and less than or equal to 50 ° C.

Hereinafter referred to as "colloidal aqueous dispersion" is the dispersion of colloidal particles in water.

Throughout the text, the preferred embodiments are applied in the same way to the two objects of the invention: the coated substrate and its method of obtaining.

The invention therefore consists in depositing on the glass substrate a weakly adherent layer simply constituted by a stack of small hard spheres in a polymer. These hard spheres that do not establish strong chemical bonds, either between themselves or with the glass surface, the layer obtained can be easily removed with the help of pure, warm or warm water, without the need to use highly basic solutions or potentially organic compounds pollutants The cohesion of the layer in spite of everything is guaranteed by weak forces, such as Van de Der Waals forces or electrostatic forces, and its resistance to abrasion and friction is remarkable. The layer according to the invention is preferably resistant to abrasion, in the sense that it resists at least 500 cycles, or even at least 2000 cycles, according to the test described in EN 1096-2, explained below in this text.

The protective layers of the prior art and obtained from aqueous dispersions of water-insoluble poftmeros instead have a fairly strong cohesion, probably due to chemical reactions of polymerization or phenomena of partial fusion and gluing of the particles, and which require the use of basic solutions or special organic products.

By "essentially constituted", it is understood that the protective layer may eventually comprise another compound, such as traces, and that it does not influence the manner in which the layer solves the technical problem at the base of the invention. Preferably, the layer according to the invention is constituted by a stack of discernible colloidal polymer particles.

The aqueous colloidal dispersion preferably consists of water and polymeric colloidal particles, with the exclusion, therefore, of any other chemical agent (such as, for example, pigments, binders, plasticizers ...). Similarly, the colloidal aqueous dispersion is preferably the only compound used to form the temporary protective layer.

Drying is carried out at a temperature higher than the glass transition temperature of the polymer to obtain a continuous layer. In fact, it was observed that below this glass transition temperature, drying was accompanied by the creation of fissures, destroying the continuous character of the protective layer. On the other hand, drying is carried out at a temperature of at least 50 ° C in order to preserve very discernible particles, which do not have coalescence between them at the time of drying. A temperature that is too high runs the risk of creating a film consisting not of small hard spheres discernible but of particles stuck together, to the detriment of the ease of subsequent disposal. The drying is preferably carried out at a temperature close to room temperature or at a slightly higher temperature, for example between 25 and 35 ° C. Preferably, no heating means (such as, for example, infrared lamps) and / or no forced drying means, such as ventilation systems, hot or cold air blowing, are used, with the exception of possibly drying means soft (at temperatures slightly above room temperature), which can use hot air drying or some infrared lamps. Heating or drying too long or too high risk in effect of forming films in which the polymer particles will no longer be discernible, but rather stick together, partially or even completely melted, the films being obtained subsequently difficult to remove. . The means of heating or of forced drying are the mayona of the useless times, since it was observed that the drying of the layers could be done very naturally in a few minutes, typically less than 3 minutes, or even less than 2 minutes.

In general, it is preferred that the shape and size of the colloidal particles are not substantially modified by drying. This characteristic is in general a proof of the absence of strong bonds between the particles, which is decisive for obtaining the desired effect of elimination with water. In general, it is obtained by rapid drying and at a temperature that is not too high with respect to the glass transition temperature of the polymer.

The average diameter of the colloidal polymer particles in the colloidal aqueous dispersion and / or in the temporal layer is preferably between 40 and 500 nm, in particular between 50 and 300 nm, and even between 80 and 250 nm.

The polymer is preferably a polymer or an acrylic copolymer, for example a styrene-acrylic copolymer. This type of poftmeros has the advantage of adhering very weakly to the glass surface, which allows an easy removal of the layer. In addition, acrylic dispersions are easily obtained by emulsion polymerization reactions that obtain particles of controlled and reproducible size. Other types of poftmeros are usable, for example polyurethanes. These poftmeros have no particular chemical affinity with silicones,

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and it was observed that silicones do not migrate and do not graft onto this type of poftmeros, which constitutes a supplementary advantage of the protection layer according to the invention.

The polymer used in the dispersion is preferably fully polymerized, in order to avoid any polymerization reaction between the different particles during drying and / or subsequently. These chemical reactions in fact undesirably increase the cohesion of the film and prevent the removal with the help of pure water.

The glass transition temperature of the or of each meter is preferably less than or equal to 30 ° C and / or greater than or equal to 20 ° C. It was observed that the glass transition temperature influences the water resistance of the layers obtained. When the glass transition temperature of the polymer is less than about 20 ° C, the layer is more easily removable with fine water. For higher glass transition temperatures (which therefore require drying at a higher temperature), the layer obtained is more resistant to cold water (and will therefore better resist precipitation), but it can be Remove with the help of warm water.

The colloidal aqueous dispersion can be deposited by different techniques, such as spraying ("flow coating"), immersion ("dip-coating"), curtain or spraying ("spray-coating").

To ensure optimum protection, the thickness of the temporary protection layer (when appropriate after drying) is preferably between 2 and 100 micrometers, in particular between 5 and 50 micrometres, or even between 10 and 30 micrometers.

The glass substrate is generally a glazing, such as a flat or convex, single or multiple glazing (double, triple ...), a tempered or annealed glazing, a colorless or tinted glazing, the thickness of which is, in particular, between 1 and 19 mm, more specifically between 2 and 10 mm, or even between 3 and 6 mm. This substrate or glazing can be coated on at least one of its faces of layers or stacks of thin layers that confer optical properties (mirrored or anti-reflective layers ...), thermal (low emission or antisolar layers, in particular, based of silver layers), electric (antistatic layers, transparent conductive layers). In this case, the temporary protection layer also protects the layers deposited on the substrate.

The protective layer may cover one of the surfaces, or the two surfaces of the glazing.

The substrate to be coated preferably includes under the temporary protection layer at least one hydrophilic layer, in particular, a layer based on photocatalytic titanium oxide. The hydrophilic layer is preferably in contact with the temporary protection layer. The hydrophilic layers are in fact the most susceptible layers to see their functionalities affected by external contamination such as silicones. The titanium oxide-based layer is preferably the last layer deposited on the substrate before deposition of the temporary protection layer according to the invention. The titanium oxide-based layer may consist of titanium oxide, deposited, in particular, by sol-gel method, chemical vapor deposition procedure (CVD) or cathode spraying process (for example magnetron procedure). The titanium oxide-based layer may alternatively be composed of titanium oxide particles incorporated in a mineral binder, for example a silica binder obtained by a sol-gel type process. The hydrophilic layer, and, in particular, if it is a layer based on photocatalytic titanium oxide, is preferably deposited on a sublayer that acts as a barrier to the migration of alkali ions, in particular, a derivative layer of silicon, such as oxide, nitride or silicon oxycarbide, or any one of their mixtures. Alternatively or cumulatively, the hydrophilic layer, in particular, based on photocatalytic titanium oxide, can be combined with other types of sub-layers, in particular, optical function layers (anti-glare, or layers that attenuate the reflection of titanium oxide), or also thermal (antisolar layers, low emissives, in particular, of the type that includes at least a thin layer of silver or a transparent conductive layer).

The protective layer according to the invention resists friction and abrasion. It can, therefore, be deposited at the time of manufacturing the glazing and resists storage, transformation, transport and installation on site. For example, the protective layer can be deposited according to the invention just after the deposition of thin layers on the glass. In the case of insulating glazing (multiple glazing, in particular double glazing or triple glazing), the protective layer according to the invention can be deposited in different phases of the transformation. Multiple glazing is obtained by assembling several sheets of glass, generally two, or even three, around a generally metallic peripheral frame, with the help of a butyl joint. This gasket on the other hand is protected by a peripheral mastiff coated on the entire section of the insulating glazing. In the case of structural insulating glazing, in the sense that these glazing is not inserted in the groove of the frame, the peripheral mast is generally made of silicone. In this case, it is preferable that the protective layer according to the invention be deposited before this coating stage to protect the hydrophilic function against silicone vapors, or just before the assembly of the sheets and the frame, or just after of this assembly. In the case of glazing intended to be inserted into frames, for example based on PVC, aluminum or wood, the peripheral mastiff is generally not silicone based. In that case, it is preferable and simpler to deposit the protective layer after the mastication coating, therefore at the last stage of the manufacturing process of the insulating glazing. It can

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alternatively deposit before assembly or coating. Thus, the insulating glazing remains protected during all the following stages: storage, transport to the site, installation on site, stages during which the glazing can be subjected to accidental contamination, in particular, of silicones.

The protective layer can be deposited on the surface of a glazing coated with a layer of photocatalytic titanium oxide, said glazing being intended to equip a double or triple glazing and the photocatalytic layer located outside the building. The temporary protection layer can be removed after on-site installation or is retained for a few weeks, as long as the multiple glazing silicone gaskets have finished emitting silicone vapors. Once this period is over, the temporary protective layer that protects the glazing against silicone vapors can be easily removed with water, fna or warm.

A subject of the invention is also a method of applying the temporary protection layer according to the invention, in which said protection layer is used to temporarily protect the glazing surface, then said temporary protection layer is removed with the help of water. fna or warm. The water is preferably pure, in the sense that it does not include organic compounds (for example detergents), or inorganic compounds (for example, ammonium salts) except for traces that are hardly avoidable. The pH of the water used is preferably between 6 and 8, in particular between 6.5 and 7.5. The pH can sometimes be less than 6, in particular, in the case of deionized water.

Of course, the various combinations of the preferred features of the invention constitute, in themselves, preferred embodiments of the invention.

The invention will be better understood in the light of the figure and the non-limiting examples that follow.

Figure 1 represents a view taken by scanning electron microscope of a cut of a glass sample covered with a protective layer according to the invention. A part of the glass substrate 1 covered with a protective layer 2 according to the invention is seen in Figure 1, where only one part is visible in the figure. The protection layer 2 is constituted by an assembly of a multitude of colloidal particles 3, perfectly discernible.

Example 1

The glass substrate to be coated is a flat glass substrate approximately 6 mm thick and obtained by a "float" type procedure (float procedure consisting of pouring the glass in fusion on a tin bath). This substrate was previously coated with a layer of silicon oxycarbide (SiOC), again coated with a layer of 15 nm thick photocatalytic titanium oxide. These two layers are obtained by a CVD-type procedure, in which organometallic precursors or halides in the gas phase are provided near in the vicinity of the hot glass band after flotation formation.

The colloidal dispersion used is an aqueous dispersion of an acrylic copolymer sold under the name NeoCryl XK-240 by the company DSM NeoResins. This dispersion is composed for 48% by weight of water and for 52% by weight of particles of an acrylic copolymer whose average diameter is approximately 180 nm (measured by known methods, which employ the diffusion of light). The glass transition temperature of the polymer is -4 ° C. The viscosity of the dispersion at 25 ° C is 160 mPa.s and its pH is 7.5.

The dispersion is deposited on the glass substrate by immersion, and after drying at room temperature without forced ventilation for a few minutes (typically 2 to 3 minutes), the layer obtained is continuous, approximately 20 micrometre thick. The light transmission of the protection layer is of the order of 88%, opacity of the order of 30%.

The layer is resistant to abrasion in the sense of EN 1096-2. The test consists of applying on a part of the coated surface of 9.4 cm in length - this part being called a track - a felt 14 mm in diameter, 10 mm thick and 0.52 g / cm2 of volumetric mass, under a load of 39.22 MPa (400 g / cm2), the felt being subjected to a translation (50 round trips on the entire track length per minute) combined with a rotation of 6 rpm (1 cycle = 1 round trip) . The layer according to the invention resists at least 2000 cycles.

The temporary protection layer can however be very easily removed by spraying pure water (no organic additives added) at room temperature.

Some tests were also carried out that allowed to characterize the contamination of silicones. These tests consist of placing the coated substrate of example 1 in contact with a silicone cord (reference Dow Corning 787s) and measuring the contact angle with water after 7 days. A parallel comparative example is also tested; It is a substrate not coated by the protective layer according to the invention. After 7 days, the contact angle with water for the comparative example goes from 30 ° to more 75 °, which testifies to a fairly strong contamination of silicone vapors. On the contrary, the contact angle with water of the sample of example 1 remains stable, below 35 °. This result clearly shows that silicone vapors are not grafted onto the protective layer according to the invention.

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Example 2

The substrate to be coated is identical to that used in the case of example 1.

The colloidal dispersion used is an aqueous dispersion of an acrylic copolymer sold under the name NeoCryl XK-87 by the company DSM NeoResins. This dispersion is composed for 49% by weight of water and for 5l% by weight of particles of a styrene-acrylic copolymer whose average diameter is approximately 210 nm. The glass transition temperature of the software is 24 ° C. The viscosity of the dispersion at 25 ° C is 250 mPa.s and its pH is 7.4.

This dispersion is applied as in the case of example 1, but drying is carried out here at 35 ° C, in order to maintain a temperature greater than the glass transition temperature of the polymer. A deposition at a lower temperature (for example 20 ° C) leads to a non-continuous layer.

The optical and friction resistance properties are similar to those of Example 1. The layer is nonetheless resistant to cold water, and can therefore resist weathering. On the other hand, the layer is easily removable with the help of warm water (approximately 30 to 35 ° C) by applying light friction with the help of a sponge or cloth.

Comparative Example

The substrate to be coated is identical to that used in the case of example 1.

The colloidal dispersion used is an aqueous dispersion of an acrylic copolymer sold under the name NeoCryl XK-52 by the company DSM NeoResins.

This dispersion is composed for 60% by weight of water and for 40% by weight of particles of an acrylic copolymer whose average diameter is approximately 70 nm. The glass transition temperature of the polymer is 115 ° C. The viscosity of the dispersion at 25 ° C is 15 mPa.s and its pH 5.1.

This dispersion is applied as in the case of example 1, and drying is carried out here at 35 ° C as in example 2. The deposition, carried out at a temperature lower than the glass transition temperature of the polymer, leads to a layer not Continuous, consisting of fields whose size is of the order of ten micrometers, separated by fissures. Such a non-continuous layer cannot effectively protect the surface of the substrate, in particular against contamination resulting from the migration of silicone vapors.

Claims (15)

5 10 fifteen twenty 25 30 35 1. - Glass substrate (1) coated with a layer of continuous temporary protection (2) removable with water, said layer (2) consisting essentially of a stack of discernible colloidal polymer particles (3). 2. - Substrate according to claim 1, such that the average diameter of the polymer particles (3) is between 40 and 500 nm. 3. - Substrate according to the preceding claim, such that the average diameter of the polymer particles (3) is between 50 and 300 nm. 4. - Substrate according to any one of the preceding claims, such that the polymer is a polymer or an acrylic copolymer. 5. - Substrate according to the preceding claim, such that the polymer is a styrene-acrylic copolymer. 6. - Substrate according to any one of the preceding claims, such that the glass transition temperature of or of each polymer is less than or equal to 30 ° C. 7. - Substrate according to any one of the preceding claims, such that the thickness of the temporary protection layer (2) is between 2 and 100 micrometers, in particular between 5 and 50 micrometers. 8. - Substrate according to any one of the preceding claims, which includes under the temporary protection layer (2) at least one hydrophilic layer. 9. - Substrate according to the preceding claim, such that the hydrophilic layer is a layer based on photocatalytic titanium oxide. 10. - Substrate, according to claim 8 or 9, such that the hydrophilic layer is deposited on a sublayer that serves as a barrier to the migration of alkali ions, in particular, a layer of oxide, nitride or silicon oxycarbide, or any one of its mixtures. 11. - Procedure of coating a glass substrate (1) by a layer of continuous temporary protection (2) removable with water, in which an aqueous dispersion of colloidal particles (3) is deposited on at least one surface of said substrate of at least one solid and water insoluble polymer, then the layer thus obtained is dried at a temperature greater than the glass transition temperature of said at least one polymer and less than or equal to 50 ° C. 12. - Processed according to any one of the preceding process claims, such that the aqueous dispersion consists of water and said polymeric colloidal particles (3). 13. - Method according to any one of the preceding process claims, such that the shape and size of the colloidal particles (3) are substantially not modified by drying. 14. - Method according to any one of the preceding process claims, such that the colloidal aqueous dispersion is deposited by spraying, immersion, to the curtain, or by spraying. 15. - Method of applying the temporary protection layer (2) described in any one of claims 1 to 10 or obtained according to any one of claims 11 to 14, wherein said protective layer (2) is used for temporarily protect the surface of glazing, then said temporary protection layer (2) is removed with the help of cold or warm water.